Prepare 3.2.0 release

CHANGES.txt

@@ -1,5 +1,5 @@
-3.2.0 (Next 3.x Release)
-------------------------
+3.2.0 (2015-11-30)
+------------------
 
 - Files included via the ``[include]`` section are read in sorted order.  In
   past versions, the order was undefined.  Patch by Ionel Cristian Mărieș.

supervisor/version.txt

@@ -1 +1 @@
-3.2.0.dev0
+3.2.0